The Heat and Thunder played only twice this season, each winning on their home court.

Wade added 23 points on Saturday with Bosh scoring 19 off the bench and role player Shane Battier contributing four key three-pointers.

"This has to be a collective group for us to win a championship, from the first guy all the way down to 15," three-times league most valuable player James said.

"Everybody was in tune today and we wanted to give our fans a big win tonight and we were able to do that."

Rajon Rondo tried to keep the aging Celtics competitive, and they were for three quarters before the Miami's Big Three took over.

"We let this one slip away," said Rondo, who finished with 22 points, 14 assists and 10 rebounds.

"We just had nothing left," said Celtics coach Doc Rivers after his team had gone deeper in the Eastern series than many had thought likely against the Heat.

Total defence

Paul Pierce added 19 points and Brandon Bass, the sparkplug of the Celtics' first half lead, finished with 16. But he had only two points in the second half as Miami cranked up their defence and turned to their Big Three for all of their fourth quarter points.

What turned out to be a nip-and-tuck third quarter ended in a 73-73 tie and after Ray Allen drilled home a three-pointer for Boston's final lead at 82-81 with 8:49 to go in the game, James and company took over.

James put Miami back up with a monster dunk, Bosh added the last of his career-best three three-pointers and James scored again, and suddenly the Heat fans were ready to celebrate.

"He was big time. Every shot, every defensive play, every defensive rebound." James said of Bosh, who played his biggest role since returning earlier in the series from a strained lower abdominal muscle.

"We missed him and are just happy to have him back at the right time."